Turburlence promoters for fluid cooled electrical apparatus



Nov. 10, 1959 K. K. PALUEV 2,912,658

TURBULENCE PROMOTERS FOR FLUID COOLED ELECTRICAL APPARATUS Filed Dec.26, 1952 2 Sheets-Sheet 1 Fig.1.

Inventor:

Konstantin K. Paluev, by @MPW Hi5 Atbonneg.

Nov. 10, 1959 K. K. PALUEV 2,912,658

TURBULENCE PROMOTERS FOR FLUID COOLED ELECTRICAL APPARATUS Filed Dec.26, 1952 2 Sheets-Sheet 2 Inventor: Konstantin K. Paluev,

His Attorneg.

1 2,912,658 TURBULENCE PROMOTERS FOR FLUID COOLED ELECTRICAL APPARATUSKonstantin K. Paluev, Pittsfield, Mass, assignor to General ElectricCompany, a corporation of New York Application December 26, 1952, SerialNo. 328,113

3 Claims. (Cl. 336-58) This invention relates to stationary electricalinduction apparatus having a magnetic core and electrical windings and,more particularly, to an improved cooling arrangement for suchapparatus.

When stationary electrical induction apparatus is operating heat isproduced. The heat produced must be removed if the apparatus is to bekept within. safe temperature limits. For instance, if the heat producedis not removed, the electrical windings may become heated to such a hightemperature as to destroy the insulation on the electrical windings.

Some installations of stationary electrical induction apparatus arefluid cooled. Cooling ducts are formed in the magnetic core andelectrical windings and cooling fluid passes through these ducts bynatural convection flow or by forced fluid flow. In forced fluid flowthe cooling fluid is forced through the cooling ducts by pumps, andtypically, the flow of fluid through the cooling ducts is laminar inorder to keep pumping costs down.

By virtue of the fact that all the heat produced in the electricalinduction apparatus must be removed, a given electrical inductionapparatus cannot be operated beyond a fixed maximum load. This isbecause the cooling systern is designed to remove what heat is producedat maximum load, and not much more. If the load is increased beyond thefixed maximum rating, the cooling system is inadequate to remove all theheat produced, and the electrical winding insulation may be destroyed.

The amount of heat that the cooling system is capable of removing cansometimes be increased by varying the cooling duct dimensions orincreasing the amount of cooling fluid circulated. However, the problemof adequate heat removal has not been found to be so relatively simple,but depends upon many considerations. Decreasing the cooling ductdimensions will increase the amount of heat that can be removed.However, electrical considerations may demand that the cooling ductdimensions be relatively large and fixed values. Increasing the amountof cooling fluid circulated will also increase the amount of heat thatcan be removed, but if the amount of cooling fluid circulated isincreased the costs of pumping the cooling fluid are concomitantlyincreased.

It is an object of my invention to provide improved cooling meanswhereby the cooling system of stationary electrical induction apparatusis capable of greater heat removal permitting operation of the apparatusbeyond maximum rated load.

It is a further object of my invention to provide improved cooling meansfor stationary electrical induction apparatus at a minumum of costwithout increasing the amount of cooling fluid circulated or varying thecooling duct dimensions.

I have discovered that in conventional stationary electrical inductionapparatus with fixed duct dimensions and rate of flow of cooling fluidthe amount of heat the cooling system is capable of removing can beincreased by the addition of turbulence promoters in the cooling ducts.

My invention consists of the introduction of appropriately placedrestrictions or turbulence promoters in the cooling ducts of stationaryelectrical induction apparatus, said promoters increasing the amount ofheat the cooling system is capable of removing without any change in thecooling duct dimensions or the amount of cooling fluid circulated.

States Patent 2,912,658 Patented Nov. 10, 1959 The addition ofturbulence promoters in the cooling ducts, where the maximum ratedoutput of the apparatus is not exceeded, has the eifect of reducing thetemperature of the apparatus. If the temperature of the apparatus isreduced, obviously, then the load on the apparatus can be safelyincreased beyond the rated output. However, my inventon is useful evenwhere it is not desired to overload the apparatus. For instance,frequently local hot spots occur in the apparatus even when theapparatus is not overloaded. It is desirable to reduce such localizedhot spots. I have discovered that the introduction of an appropriatelyspaced continuous restriction in the area of the localized hot spot willreduce hot-spot temperature.

Therefore, my invention also consists of the introduction ofappropriately placed restrictions in the cooling ducts to reducelocalized hot spots.

My invention has numerous advantages. For instance, the amount of heatthat can be removed by the cooling system of any given stationaryelectrical induction apparatus can be increased at a slight cost, ascontrasted to the high costs of altering the cooling duct dimensions orincreasing the amount of cooling fluid circulated. With my improvedcooling means, due to the fact that the amount of heat removed by thecooling system of a given stationary electrical induction apparatus canbe increased, the rated safe output in a given electrical inductionapparatus can be safely exceeded. That is, at a minimum of cost, thesafe operating load of an apparatus can be exceeded without harm to theapparatus. Conversely, my invention permits a reduction in the size ofstationary electrical apparatus. With my invention, because the amountof heat removed can be increased, a smaller apparatus with turbulencepromoters will give the output of a larger apparatus with unrestrictedcooling ducts.

The features of my invention which I believe to be novel are set forthwith particularity in the appended claims. My invention itself, however,both as to its organization and use, together with further objects andadvantages thereof, may be best understood by reference to the followingdescription and accompanying drawings.

In the drawings, Figure 1 represents a sectional View of one form of myinvention as applied to a stationary electrical induction apparatushaving a magnetic core and barrel-type windings. Figure 2 is a view inperspective of the turbulence promoters used in the electrical windingscooling ducts of Figure 1. Figure 3 is a view in perspective of theturbulence promoters used in the core cooling ducts of Figure 1. Figure4 is another embodiment of my invention wherein the legs of anintegrally interconnected series of U-shaped sections serve as theturbulence promoters. Figure 5 is still another modified type of fluidflow restriction in which the turbulence promoter is spirally wrapped.Figure 6 is a view of a sleeve arrangement for producing increasedcooling in a localized region to reduce hot spots. Figure 7 is asectional view of my invention as applied to a stationary electricalinduction apparatus with disc windings. Figure 8 is a view of myinvent-ion as applied to helical electrical windings.

Referring now to the form of the invention illustrated in Figures 1 to3, there is shown in Figure l a sectional view of a stationaryelectrical induction apparatus, which in this case is a transformer 1enclosed in a casing or tank structure 2. Inside of the casing 2 ispositioned a magnetic core 3, around each of the winding legs of whichare positioned a plurality of electrical windings. An insulating barrierin the form of a cylinder 4 surrounds each leg of the magnetic core, andan electrical winding 5 of the barrel type is positioned radiallyoutward of insulating cylinder 4 and is separated therefrom by an axialduct 6. A second insulating cylinder 7 is positioned radially outward ofbarrel winding and is separated from winding 5 by an axially extendingduct 8. A second barrel-type winding 9 is positioned radially outward ofinsulating cylinder 7 and is separated from insulating cylinder 7 by anaxially eX- tending duct iii. A third insulating cylinder 11 ispositioned radially outward of winding 9 and spaced therefrom by anaxially extending duct 12. Thus, it is seen that the plurality ofelectrical windings and insulating barriers are spaced from each otherin concentric telescopic fashion, with the surfaces of the electricalwindings being spaced from adjacent insulating barrier surfaces to formcooling ducts.

The windings and insulating cylinders are supported at their lower endsby a suitable support member 13, which may be a metal member conformingat its radially inner portion to theperipheral outline of the core legs,and at its radially outer portion to the peripheral outline of the tankstructure. An inlet pipe 14 is provided at the lower end of the tankstructure and is the means by which a fluid insulating and coolingmedium is admitted to the lower portion of the tank from a heatexchanger, not shown- An outlet pipe 15 is provided at the upper end ofthe tank and is the means by which the cooling and insulating fluidleaves the talk to the heat exchanger. Suitable apertures 16 areprovided in the support member 13 to conform with the ducts 6, 8, 19,and 12. and are the means by which the cooling and insulating fluidpasses from the lower portion of the tank up into the ducts between thewindings and insulatin g barriers.

in accordance with my invention, I provide a restrictive arrangement inthe ducts which permits a much greater cooling effect for a duct of agiven radial thickness and for a given volumetric time rate of flow ofcooling and insulating fluid than is attainable in unrestricted ducts.The restrictive means comprises annular members 17 which may be made ofany suitable insulating material. By the term annular I include anyrestrictive member interposed in the cooling ducts and conforming to thecontours of the ducts. For instance, the ducts may be circular,rectangular, or oval in cross section. Accordingly, annular members 17will conform to the circular, rectangular or oval outline of the ducts.Furthermore, the annular restrictions need not necessarily extendcontinuously in one piece around the periphcry of the ducts, but insteadmay be discontinuous.

The annular members 17 abut against the surfaces of the insulatingcylinders. However, the annular members 17 can also be arranged to abutthe windings instead of the insulating cylinders. a

As will be best seen in Figure 2, the annular membe'rs 17 pass through,by virtue of notches 19, and are supported by axially extending spacermembers 13 which are positioned circumferentially in the ducts. Thespacer members also serve to properly radially space the insulatingcylinders 4 and windings 5.

it will be obvious that the promoters need not always abut theinsulating cylinders. For instance, one prometer may abut theinsulatingcylinder, and the next succeeding promoter may abut the electricalWinding. This can be readily accomplished by forming notches 19 first onthe face of spacer 18 facing the insulating barrier 4 and then on theface of spacer 18 facing the winding 5. middle of the duct. That is,supporting holes for the promoters can be formed in the spacers between.posite sides thereof so that the promoters lie in ddle of the duct anddo not abut either the insulating cylinder t or electrical winding 5.

in Figures 2 and 2 the cooling ducts are formed by an electrical windingand an adjacent but spaced insulating barrier. However, my invention isalso appli- Also, the promoters can be mounted'in the.

A cable where two electrical windings are spaced from each other byaxial spacers and form a cooling duct therebetween.

Referring again to Figure 1, it will 'be noted that the core 3 also hascooling ducts Zii formed therein. Magnetic cores are conventionallyformed out of laminated metal sheets. Spacing the laminations providescooling ducts 20. As in the electrical windings, turbulence promoters 21are provided in the cooling ducts the magnetic core. As shown in Figure3, in conventional transformers, the laminations forming the core legand the cooling ducts typically are spaced by buttons or lugs 22. Theturbulence promoters 21 are metal strips welded to one of thelaminations. The cooling fluid which enters tank 2, Figure 1, throughinlet 14 passes beneath the lower flange of supporting plate 13 and thenenters the core cooling ducts 2i Eventually the cooling fluid leaves theducts 29 at' the top of the magnetic core and passes out of tank 2through exit pipe 15 to the heat exchanger, not shown.

There is shown in Figure 4 a modified structure which may be used inplace of the annular restriction members 17 and spacers 18 of Figures 1and 2. In Figure 4 a plurality of spacer and restriction members are inabutting relation to the outer surface of an insulating cylinder 23 andalso in abutting relation to the radially inner surface of a windingwhich is not shown. Each spacer and restriction member is a stripcomprising a series of alternating portions 24 and 25, with the width ofportions 24 equal to the width of the duct and the width of portions 25equal to the restriction which is to be placed in the duct. Portions 25are bent so as to extend circumferentially around the cylinder 23.Portions 24 extend parallel to each other in the axial direction, andany.v

two immediately succeeding portions 24 are spaced circumferentially.

Viewed in another manner, each strip is a series of integrallyinterconnected U-shaped sections. The bases 24 0f the U-shaped sectionsserve as axially extending spacer members, and the legs 25 of theU-shaped sections, suitably cut out to the desired restrictiondimensions, serve as the transversely extending restriction members.Each of the ducts has a plurality of such strips circumferentiallyspaced therein.

Each of the portions or members 24- is provided with a circumferentiallyprotruding tab 26, and an axial member 27 overlies tabs 26 and bearsagainst the portions 24 to help maintain the strips in position.

There is shown in Figure 5 another embodiment of my invention. In thisembodiment the duct restriction is in the form of a spirally woundmember28. The member 28 is supported by axial spacer members 29 which alsospace insulating cylinder 40 and electrical winding 41.

There is shown in Figure 6 a further modification in which the ductrestriction is in the form of at least one sleeve member 45. The sleevemember 45 differs from the turbulence producing restrictions previouslydescribed in that the length of the restriction member 45 isconsiderably greater than the duct width, and has particular utility inconnection with temperature reduction of localized hot spots. As inprior embodiments, the restriction members 45 are supported by axialspacer members 43 which also space insulating cylinder 42 and electricalwindings 44.

There is shown in Figure 7 another application of my invention. In thisinstance the electrical windings are of the disc type. In the disc typeof electrical winding a single conductor is wound radially outward intoa plurality of discs 34 and the discs are stacked on top of each other.Separating the disc windings are insulating discs 32. Members 30 and 31are cylindrical insulating cylinders. The stacked discs 34 andinsulating cylinder 31 define a cooling duct 35. Each alternate disc 33is larger than disc 32 and protrudes into the cooling duct and serves asthe turbulence promoter. As in prior embodiments axial spacers spaceinsulating cylinder 31 and the stacked discs 34 and are suitably cut outto receive the protruding turbulence promoters 33.

In Figure 8 is illustrated a helical electrical winding and my inventionapplied thereto. In a helical electrical winding a plurality ofelectrical conductors are simultaneously spirally wound on an insulatingbarrier. In Figure 8 the electrical winding 36 is wound on insulatingbarrier 37 with adjacent turns of the electrical winding spaced byinsulating disc material. Protruding turbulence promoter 38 is wound forone turn, every other turn of the insulating disc material. One of theaxial spacers 39 is suitably notched to receive the ends of each turn ofpromoter disc 38. If the axial spacer 39 were not present, the coolingfluid would have a tendency to pass through the openings defined by thespaced ends of each turn of promoter 38. The axial spacer 39 prohibitsthis and forces the cooling fluid to pass over the promoters. Also,spacers 39 axially space windings 36 and an adjacent insulating barrier,not shown, to form the cooling duct.

In an unrestricted cooling duct the cooling fluid has a velocity in theaxial or longitudinal direction of the duct. As before stated, inconventional cooling systems, the flow of fluid typically is laminar.This is because electrical considerations demand that the duct width berelatively large and in order to keep pumping costs down, the fluid isforced through the cooling ducts at a relatively small velocity. In thepractice of my invention, the only change made over conventional coolingsystems is the addition of turbulence promoters. There is no change madein the duct dimensions or quantity of cooling fluid circulated per unittime. With such a slight modification at a very low cost, the output oftransformers embodying my invention may be safely increased beyondpresent maximum ratings. My turbulence promoters make this possible byproducing turbulence within the cooling ducts. That is, besides avelocity component in the axial direction, there is a velocity componentin the radial direction. Thus, the relatively hot cooling fluid adjacentto the electrical windings by turbulence is caused to mix with therelatively cooler cooling fluid further removed from the surface of theelectrical windings. Simultaneously, the relatively cooler fluid has anopportunity to reach the winding surfaces. Because of this, a coolingsystem embodying my invention is capable of removing more heat and coolsthe electrical windings. My invention can be used to reduce windingsurface temperature when no increase in rated output of the electricalinduction apparatus is contemplated. For instance, hot spots can bereduced. Also, if the electrical winding temperature can be reduced itis possible to use a cheaper grade of insulation for the electricalwindings. A still more profitable use of my increased cooling effect isto increase the rated output of conventional transformers withoutexceeding permissible electrical winding temperatures. Also, with myimproved cooling system a smaller transformer can give the output of alarger transformer with unrestricted cooling ducts. That is, a saving inspace and weight can be realized.

It is also within the contemplation of my invention to grade mypromoters. The downstream temperature of the cooling fluid is obviouslyhigher than the temperature of the cooling fluid near the inlet to thecooling ducts. Consequently, as one progresses downstream in the coolingducts, the promoters can be made progressively wider toobtain greaterturbulence.

The distance between two succeeding promoters should preferably be suchthat the second promoter will cause turbulence before the turbulencepromoted by the first promoter has, lost its effectiveness. If thepromoters are too close together turbulence will not be induced, but theflow of fluid will be laminar and fluid will tend to stagnate betweenpromoters. it the promoters are too far apart, laminar flow will beestablished before the next promoter is reached.

Disclosed are various embodiments of my invention as applied to barrel,disc, and helical electrical windings. Also the windings and insulatingcylinders have been shown as being of a cylindrical configuration.However, my invention can be applied to oval or rectangular windings andinsulating cylinders. Also, it will be obvious that the describedembodiments are illustrative only of my invention and that other formsof spacers and turbulence promoters and methods of practicing myinvention can be used. Therefore, I do not intend to be limited by theforms disclosed. What I believe to be my invention I have set forth withparticularity in the appended claims.

What I claim as new and desire to secure by Letters Parent of the UnitedStates is:

1. In an electrical induction apparatus having a plurality ofbarrel-type electrical windings, cooling means for said windingscomprising insulating barriers alternated with said windings andtelescopically spaced from adjacent winding surfaces to form a pluralityof axially extending cooling ducts, axially extending spacer memberscircumferentially located in said ducts and abutting adjacent insulatingbarrier and winding surfaces to radially space them, means for forcing acooling fluid through said ducts at low velocity, means in said ductsfor increasing the the amount of heat that can be removed from thesurface of said windings by periodically causing turbulent flow, saidlast mentioned means comprising transverse extending turbulencepromoting members partially obstructing said ducts and periodicallylocated along the length of said ducts, said transverse members being soproportioned relative to the duct widths as to periodically produceturbulent flow, said transverse members in said ducts supported by saidaxially extending spacer members.

2. In an electrical induction apparatus as in claim 1, wherein saidtransverse turbulence promoting members are continuous annular ringslying in planes perpendicular to the axis of said ducts, a plurality ofsaid rings periodically located along the length of each of said ducts.

3. In a fluid cooled electrical induction apparatus having a pluralityof barrel-type electrical windings cooling means for the windings,comprising a plurality of insulating barriers telescoped with theelectrical windings and concentric therewith, each insulating barriersurface being spaced from the adjacent electrical winding surface toform an axially extending cooling duct therebetween, means for producinga flow of cooling fluid in said ducts, restriction means in the ductspartially obstructing said ducts and adapted to periodically produce avelocity component of said fluid perpendicular to said windings, andaxially extending spacer members spacing the adjacent surfaces of thewindings and insulating barriers, said restriction means comprisingtransverse members conforming to the peripheral contours of the ductsand supported therein by said axially extending spacer members, saidtransverse members comprising a plurality of rings, conforming to theperipheral outline of said ducts and lying in a plane normal to the axisof said ducts, the rings within each duct being spaced along the lengththereof.

References Cited in the file of this patent UNITED STATES PATENTS1,141,199 Moody June 1, 1915 2,339,625 De Blieux Ian. 18, 1944 2,388,566Paluev 'Nov. 6, 1945 FOREIGN PATENTS 405,512 France Jan. 6, 1910 493,431France Aug. 8, 1919 353,774 Germany May 30, 1922 269,933 Great BritainFeb. 2, 1928 235,837 Switzerland May 16, 1945

